Electron gun



y 21, 1963 s. c. MORSE 3,090,884

ELECTRON GUN Filed March 7, 1960 INVENTOR. GEORGE C. MORSE BY 2 Kfizz/@244 ATTORNEYS United States Patent C 3,090,884 ELEQTRGN GUN GeorgeC. Morse, Woodside, Calif, assignor to Eitel McCullough, inc, San Bruno,Calii, a corporation of California Filed Mar. 7, 196b, Ser. No. 13,92li6 Claims. (Cl. 3l3256) The invention relates to electron guns, andparticularly to a ruggedized electron gun.

One of the objects of the invention is the provision of an electron gunin which the electrode structure is integrally united as by brazing tothe envelope.

Another object of the invention is the provision of an electron gunconstruction in which the portion of the tube envelope enclosing theelectron gun forms an end cap for the tube and rigidly supports theelectron gun elements.

A still further object of the invention is the provision of an electrongun in which the parts may be integrally united into a compositeassembly in one operation.

A still further object of the invention is the provision of an electrongun in which the electrode elements are protected against, and areunaffected by, vibration and impact shocks.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing will be set forth in the following descriptionof the invention. It is to be understood that the invention is notlimited to the embodiment disclosed, as variant embodiments may beadopted within the scope of the appended claims.

Broadly considered, the invention comprises an electron gun in which aportion of the evacuated envelope is utilized to enclose and rigidlysupport the electron gun elements. Thus, a cylindrical wall portion isintegrally and hermetically united to a support plate portion to form anend cap for the evacuated envelope. Supported within the end cap thusformed is an electron emitting assembly including cathode and heater,both of which are integrally united to the end cap. Also enclosed andrigidly supported on and within the end cap is a focusing electrode.

Means are provided on the support plate for orienting and integrallyuniting the support plate to each element of the electron emittingassembly and focusing electrode. Apertures in the end cap provide accessto the interior of the envelope for terminal leads connected at theirinnor ends to selected electron gun elements and at their outer endsforming terminal leads outside the envelope. At its end remote from thesupport plate, the cylindrical wall portion is integrally andhermetically united to an accelerating anode. The accelerating anode iscooperatively interposed between the gun assembly and the radiofrequencystructure to which the electron gun is secured.

Referring to the drawings: FIGURE 1 is a vertical half sectional view.

FIGURE 2 is a plan View of the support plate taken in the directionindicated by the arrows on the line 22 in FIGURE 1.

FiGURE 3 is a bottom plan view taken in the direction indicated by thearrow 3 in FIGURE 1.

FIGURE 1 is drawn to a scale approximately twice ac tual size, andFIGURES 2 and 3 are drawn approximately actual size.

In greater detail, the electron gun is adapted to be integrally andhermetically attached as the end portion or cap or" an evacuatedenvelope generally designated by the numeral 2, and only a portion ofwhich is shown for purposes of description. The electron gun comprises acylindrical wall portion 3, preferably formed of dielectric materialsuch as alumina, across one metalized end of which is integrally andhermetically brazed a support plate 4, also preferably formed ofdielectric material. The cylindrical dielectric wall portion 3 ismetalized across its opposite end surfaces in a manner well known in theart, while the dielectric support plate 4 is provided with a pluralityof metalized surface areas 6, 7 and 8. As shown best in FIGURE 2, theperipheral metalized surface area 8 is a continuous circular area, whilethe metalized surface areas 6 and 7 are arcuate, each terminating atpoints spaced on opposite sides of an associated aperture. Apertures 9and 12 are related respectively, with metalized surface areas 6 and 7,and cooperate with these metalized areas in a manner to be hereafterdescribed. Aperture 13, lying within the unmetalized surface areadefined by the arcuate metalized surface area 6, extends through thesupport plate, as do apertures 9 and 12, and on the opposite side of thesupport plate each of the apertures is surrounded by a metalized surfacearea 14, shown best in FIGURE 3. Also shown best in FIG- URE 3, is theperipheral metalized surface area '16 similar to the metalized area 8but on the opposite side of the support plate.

Concentrically arranged within the cylindrical wall portion 3 andsupported on the plate 4, is an electron emitting assembly designatedgenerally by the numeral 1'7, and including a cathode 18 adapted to beheated by a heating coil 19. The cathode-heater assembly is supported ona hollow metallic shell structure 21, which at its outer end 22 isprovided with a flange 23 integrally brazed to the arcuate metalizedsurface area 6. As shown in FIGURE 1, the hollow metallic shell 21conveniently comprises an upper generally cylindrical portion 24 havingapertures 26 therein, and a lower hollow conical section 27. While theupper cylindrical portion and the lower conical section have been shownas two separate parts having their adjacent overlapping ends integrallybrazed as at 28, it will be apparent that shell structure 21 may befabricated from a single piece. It will thus be seen that the hollowmetallic shell 21, :brazcd at its broad end 22 to the metalized surfacearea 6 on the support plate, provides a very rigid construction adaptedto support the cathode and heater assembly in a manner preventingmovement of these elements by vibration or shock. Ad ditionally, thehollow metallic shell 21 provides a convenient means of conductingelectrical energy between the heater coil and its source of supply.Also, the hollow shell 2%, fabricated preferably from thin gaugematerial, provides a convenient means of preventing the conduction ofheat away from the cathode. This function is further aided by theprovision of a hollow cylindrical shell 29 of Kovar, integrallyinterposed between the upper end portion of tubular shell 24 and thecathode. This shell functions as a heat dam to prevent the flow of heataway from the cathode.

Concentrically arranged within the hollow heat dam 29 are a plurality ofsuperimposed radiating heat shields St). The heat shields are of amaterial and shape to radiate heat from the heater coil back toward thecathode, thus increasing the efiiciency of the electron gun. To supportthe heat shields in spaced superimposed relation, each of the heatshields is provided with a dimple 31 struck from the material of theshield and extending downwardly to abut the upper surface of the nextlower heat shield. The assembly of heat shields is rigidly retained inposition below the heater coil by a supporting battle plate 32, having aperipheral flange 33 integrally welded to the inner surface of thehollow heat dam shell 29.

Dielectric bushings 34, extending through apertures in the heat shieldsand supporting bafile plate 32, provide means for passage of electricalleads 36 connecting the ends of heater coil 19. One end of the heatercoil lead 36 accuses extends through a bushing 34 and is brazed at itsouter end to one end of a strip conductor 37, which is in turn brazed atits other end to the inner surface of flange 33. The other end of heaterlead 36 is integrally brazed within one end of tube 38, which extendsoutwardly through aperture '13. On its end exterior to the support plate4, the tube 38 is provided with a terminal cap 39, closed at its outerend 4 1, and having a radially extending flange 42 at its opposite end.The flange 42 is integrally and hermetica'lly brazed to the annularmetalized surface area 14 surrounding the aperture 13. A metal plug 43within the terminal cap is integrally brazed to the exterior end of thetube 38 and to the interior surfaces of the cap to provide anelectrically conductive path for the terminal lead 36. It will thus beseen that the terminal cap provides an hermetic seal about the aperture13, and also functions to provide 'a convenient electrical connection toa source of power. Such connection may conveniently be made by springclips (not shown) arranged to resiliently. engage the terminal cap. Asimilar construction, shown in elevation in FIGURE 1, serves toelectrically connect the other end of the heater coil to ground. in thiscase the inner end of tube 38 terminates at and is brazed to the flange23 on the conical shell portion 27, thus making an electrical connectionthrough the supporting shell 21. If desired, the flange 23 may beapertured to receive the end of the tube, which would then also aid inorienting the shell on the associated metalized area. To strengthen thehermetic union between the flanges 42 and the associated metalizedsurface areas 14, a backing cylinder 44 of ceramic is provided about theterminal cap 39. The cylinder of ceramic 44 is brazed at one end to theopposite side of the flanges 42 from the support plate. Stresses onopposite sides of the flanges are thus equalized and a long life isassured for the hermetic seal at this point.

Concentrically enclosed within the cylindrical dielectric wall portion 3is a second hollow metallic shell 46. This shell includes the focusingelectrode for the electron gun, and comprises an upper tubular portion47, having an indentation 48 intermediate its ends, and a lower conicalsection 49 having an outwardly extending flange 51 at its lower endintegrally brazed to the arcuate metalized surface area 7 on the supportplate 4. At its free inner end the focusing electrode is provided with arolled-over edge '2, providing a smooth contour to prevent the formationof an arc between the focusing electrode and the surrounding elements ofthe electron gun. As with the hollow metallic shell 21, the focusingelectrode shell 46 is shown to be fabricated in two pieces 47 and 49integrally joined at overlap 53. It is apparent that instead of beingfabricated in two pieces the shell 46 may be fabricated in a singleunit. The indentation 48 in the focusing electrode cooperates with thecathode to converge the electron beam in the desired degree anddirection. Alternately, instead of being an indentation in the materialof the shell itself, a short hollow cylinder (not shown) may be brazedwithin the upper portion 47 of the shell in place of the indentation toeffect the same purpose.

'It will thus be seen that when the shell 46 is integrally brazed to thearcuate metalized surface area 7 on the support plate 4-, the broad baseof the shell cooperates by the integral nature of its union with thesupporting plate to provide a rigid and vibration-free construction. Itwill also. be apparent that the parts are adapted to be fabricated incomposite units such as focusing electrode and electron emittingassembly, and the units then arranged within the cylindrical dielectricportion 3 on the plate 4 and the units oven-brazed in a singleoperation. To connect the focus electrode -46 to a source of energy, aterminal cap 39 as previously described, is brazed on the metalizedsurface area 14 associated with the aperture 12. A lead (not shown)extending from the terminal cap 39 through the aperture 12, isintegrally brazed at its inner end to the flange 51 and forms aconductive path for energy from a source not shown. To support theelectron gun in an appropriate socket, a cylindrical metallic flange 54is provided integrally brazed to the annular surface area 16 on thebottom side of the support plate 4. A measure of resilience is providedin the flange by dividing the flange into circumferentially spacedsegments by means of vertical slots 55.

integrally united to the inner end of the cylindrical dielectric Wallportion 3, is an accelerating electrodeor anode assembly 56. Theaccelerating anode comprises a radially extending annular web 57, havinga portion 58 of reduced thickness adjacent its outer peripheryinterposedbetween web 57 and terminal ring 59, and an annular recess 65 positionedopposite the rolled edge 5-2 of the focusing electrode 46. Theaccelerating anode lies in axially spaced relation to the focusingelectrode 46 and the electron emitting assembly, and is integrally andhermetically brazed adjacent its outer periphery to the associated endof the cylindrical dielectric wall portion 3. A short drift tube section61 is integrally brazed Within the inner periphcry of the web 57.

To hermetically unite the accelerating anode to the end of the cylinder3, a cylindrical flange 62 is provided with a radially extendingintegral annular flange 63, brazed adjacent its inner periphery to themetalized end of dielectric cylinder 3. The cylindrical flange 62 liessnugly within a cylindrical sleeve 6d integrally and hermetically brazedat one end to the peripheral terminal ring portion 59 of theaccelerating anode 56, and at its other end 65 integrally andhermetically heliarc welded to the cylindrical flange 62. An integraland hermetic union is thus formed between the accelerating anode and theend of the cylinder 3 which may be subsequently opened to permit removalof the gun for repairs. As with the flanges 42 on terminal caps 39, ashort cylindrical ceramic section 66 is brazed to the opposite side ofthe flange 63 in axial alignment with dielectric cylinder 3. Ceramicsection 66 equalizes the stresses imposed on flange 63 by expansion andcontraction of the parts due to extremes in temperature. The free end ofthe ceramic section 66 slidably abuts the inner surface of theaccelerating anode portion 58. The other side of the accelerating anode56 is integrally and hermetically sealed in like manner to the adjacentend of the envelope 2. As shown, a flange 67 brazed at one end acrossthe end of the envelope portion 2, cooperates with a second flange 68brazed at one end to the accelerating anode 56. Heliarc welding theflanges 67 and 68, as at the edge 69, hermetically seals the union ofthe two flanges at this point, while providing a joint which may be subsequently opened.

From theforegoing it will be apparent that a rugged and economicallymanufacturable gun construction has been provided. The cylindrical andconical cross sections of the parts render them inherently strong, andthe integral interconnection as by brazing and welding renders themunaffected by vibration and shock.

I claim:

1. In an electron gun for an electron tube having an evacuated envelope,the combination comprising an apertured dielectric support plate forminga portion of the envelope wall, a plurality of metalized surface areasarranged on at least one side of said dielectric plate, and an electronemitting assembly including a cathode having a concave emitting surfacesupported on said dielectric plate and integrally brazed to a selectedone of said metalized surface areas.

2. The combination according to claim :1, in which a focus electrode isprovided supported on said dielectric support plate and is integrallybrazed to a second one of said metalized surface areas.

3. The combination according to claim 1, in which a hollow cylindricaldielectric wall portion open at-both ends is provided supported on saiddielectric support plate and extending about said electron emittingassembly, one end of said cylindrical dielectric wall portion beingbrazed to a third one of said metalized surface areas.

4. The combination according to claim 3, in which an accelerating anodeis integrally and hermetically brazed on the end of said cylindricaldielectric wall portion remote from said dielectric support plate.

5. In an electron beam tube having an evacuated envelope, thecombination comprising an end cap constituting a portion of the envelopewall and including a hollow dielectric cylindrical Wall portion open atone end and a dielectric support plate portion closing the other endthereof, an electron emitting assembly mounted on said support plate, afocus electrode mounted on said support plate and operatively associatedwith the emitting assembly to focus electrons into a beam, and anaperture/d anode hermetically sealed to the open end of said end cap inoperative relation to said emitting assembly to effect projection of abeam of electrons through the open end of the end cap.

6. The combination according to claim 5, in which the mounting of saidemitting assembly and focus electrode on the support plate comprises twospaced arcuate metalizing layers on the inner surface of said supportplate, a tubular metallic support shell for said emitting assembly, atubular metallic support shell for said focus electrode, the base ofeach of said shells having a radially extending flange seated on one ofsaid metalizing layers, and a metallic bond joining each of said flangesto its respective metalizing layer.

References Cited in the file of this patent UNITED STATES PATENTS2,883,575 Wilson Apr. 21, 1959 2,910,607 McCullough Oct. 27, 19592,956,192 Heil Oct. 11, 1960

5. IN AN ELECTRON BEAM TUBE HAVING AN EVACUATED ENVELOPE, THECOMBINATION COMPRISING AN END CAP CONSTITUTING A PORTION OF THE ENVELOPEWALL AND INCLUDING A HOLLOW DIELECTRIC CYLINDRICAL WALL PORTION OPEN ATONE END AND A DIELECTRIC SUPPORT PLATE PORTION CLOSING THE OTHER ENDTHEREOF, AN ELECTRON EMITTING ASSEMBLY MOUNTED ON SAID SUPPORT PLATE, AFOCUS ELECTRODE MOUNTED ON SAID SUPPORT PLATE AND OPERATIVELY ASSOCIATEDWITH THE EMITTING ASSEMBLY TO FOCUS ELECTRONS INTO A BEAM, AND ANAPERTURED ANODE HERMETICALLY SEALED TO THE OPEN END OF SAID END CAP INOPERATIVE RELATION TO SAID EMITTING ASSEMBLY TO EFFECT PROJECTION OF ABEAM OF ELECTRONS THROUGH THE OPEN END OF THE END CAP.